Isaiah leaves, and Hezekiah turns his face to the wall and asks God to remember his good deeds and his wholehearted walk, then weeps bitterly. Immediately Isaiah receives another word from The Lord, before he has even left the palace, and must turn around and deliver a new, completely different message to the king. Now, the King will live another 15 years, and Jerusalem will not fall to Assyria. Hezekiah is astounded, and asks, like Gideon, for a miraculous sign, and is given one.
So what just happened here? We have what appears to be a clear cut, unequivocal announcement of death, through the prophet Isaiah no less, followed by its retraction, in response to prayers and tears. Did God change his mind?
According to the most basic and straightforward sense of that question, the answer is clearly, "Yes, He did." As a human being, interacting with another person, this is in every way meaningful to me a case of God's changing His mind. At 1:00PM (let's say), God tells Hezekiah that he will die from this illness, and at 1:30 He tells him that he will live. God pronounces the future, a human weeps and prays, and God pronounces a different future. From Hezekiah's perspective, from Isaiah's who had to go back, from any human's perspective in that palace, God had changed his mind.
(Let me insert here the practical encouragement this affords. Even when it appears that God has pronounced doom upon us, even via a prophet, yet that doom may be changed by our prayers and tears. Not only the things we don't know may change, but even the things that we believe we have heard "straight from a prophet" may change with prayer. Mercy may be found even after pronouncement of the sentence.) This is mind-boggling.
Now for the boggle....
Perhaps it is presuming too much to say that God had changed his mind. However, He certainly changed his message to Isaiah and Hezekiah. Did He not speak His mind the first time? If not, then in what sense are we to interpret His messages to us, even his explicit prophecies? Notice that this is not the only time such a thing happens. Remember Jonah, who carried God's message all over Ninevah, that it would be destroyed in 40 days, only to find that after they repented the message was changed to one of mercy. Jonah actually expected Him to change his message (or mind): that's why He didn't want to carry the message in the first place! What does God mean when he speaks to us of the future?
Without time there can be no change. Without change, perhaps, there can be no meaning to time. God is always the same, which fits with his being eternal, ie, not affected by, perhaps not even in, Time. We, however, live in time so fundamentally that we cannot imagine the world apart from time. Do you think of movement? That implies time. Of growth? That implies time. Of speech? Music? Rhythm? Sound? Stories? All these require time to make any sense at all to us. We are swept along always by time, and cannot comprehend being otherwise.
So what is God doing when He speaks to us of the future? He is representing something to us that He knows but that we can never see "from here". The future is an idea in our minds that is always changeable, always speculative, never fixed until it ceases to be tomorrow and becomes today. He sees the end from the beginning, but we can never see in that way, being by nature creatures in time even before our fall. Perhaps when God speaks to us of the future, he is communicating to us specific ideas that are as real as such ideas can be to temporal beings. We consider and respond to those ideas, and in so doing, we change. As we change, our relationship to the unchanging God and to the world He has made also changes. The change comes from us, not from God.
Face it, we do not understand time. When we think of the future, we perhaps think of it as something that is fixed by a chain of causality that we just can't see but which is there nonetheless, and quite impersonal. But perhaps that is wrong, or at least incomplete. Perhaps personal beings are the most fundamental things, and time is a created dimension or context for such beings as we are, a medium so to speak, which both we and God use to express our mutual relationships. In that case, change is fundamental to our very existence and to our relationship with God, and the future, from our perspective, is always being changed. When God re-pronounces the future, perhaps He is simply re-announcing the future that has changed as a result of our changing.